Ion mobility spectrometry (IMS) utilizes relative low electric fields to propel ions through a drift gas chamber and separate these ions according to their drift velocity. In IMS, the ion drift velocity is proportional to the field strength and thus an ion's mobility (K) is independent of the applied field. In the IMS both analyte and background molecules are typically ionized using radioactive alpha or beta emitters and the ions are injected into a drift tube with a constant low electric field (300 V/cm or less) where they are separated on the basis of their drift velocity and hence their mobility. The mobility is governed by the ion collisions with the drift gas molecules flowing in the opposite direction. The ion-molecule collision cross section depends on the size, the shape, the charge, and the mass of the ion relative to the mass of the drift gas molecule. The resulting chromatogram is compared to a library of known patterns to identify the substance collected. Since the collision cross section depends on more than one ion characteristic, peak identification is not unique. IMS systems measure a secondary and less specific property of the target molecule—the time it takes for the ionized molecule to drift through a tube filled with a viscous gas under an electric field—and the identity of the molecule is inferred from the intensity vs time spectrum.
Other mobility-based separation techniques include high-field asymmetric waveform ion mobility spectrometry (FAIMS) also known as Differential Mobility Spectrometry (DMS). FAIMS or DMS is a detection technology which can operate at atmospheric pressure to separate and detect ions. Compared to conventional ion mobility, FAIMS/DMS devices operate at much higher fields (˜10,000 V/cm) where ion mobilities become dependent on the applied field. FAIMS/DMS devices may operate in conjunction with IMS drift tube devices in spectrometers having multiple stages. For specific descriptions of features and uses of instruments for ion detection and chemical analysis, including features of IMS drift tube devices used in connection with one or more FAIMS/DMS devices, among other components, reference is made to U.S. Pat. No. 8,173,959 B1 to Boumsellek et al., entitled “Real-Time Trace Detection by High Field and Low Field Ion Mobility and Mass Spectrometry,” U.S. Pub. No. 2012/0273669 A1 to Ivashin et al., entitled “Chemical Analysis Using Hyphenated Low and High Field Ion Mobility,” and U.S. Pub. No. 2012/0326020 A1 to Ivashin et al., entitled “Ion Mobility Spectrometer Device with Embedded FAIMS,” which are all incorporated herein by reference.
Known IMS device construction techniques include the use of alternate stacking of metallic and insulator rings to produce sensor structures. These sensors structures, such as IMS drift tubes, are used in the ion transport and analysis applications at atmospheric or near atmospheric pressure. Further, other techniques are known for producing IMS sensor structures using ceramic material rolling processes. For example, U.S. Pat. No. 7,155,812 B1 to Peterson et al., entitled “Method for Producing a Tube,” and which is incorporated herein by reference, discloses a process of rolling a pliable green (i.e. prefired) ceramic sheet around a form for multiple revolutions and in which electrical conductors are disposed on a surface of the ceramic sheet. The rolled ceramic sheet is subject to pressure and fired to produce the IMS drift tube. The ceramic may be a low temperature co-fired ceramic (LTCC). It is noted that in some cases use of a continuously rolled sheet process may limit the functionality and complexity of circuit or sensor components of the IMS drift tube. Other techniques for producing three-dimensional ceramic circuit structures are described in U.S. Pat. No. 6,527,890 to Briscoe et al., U.S. Pat. No. 5,028,473 to Vitriol et al., U.S. Pat. No. 4,475,967 to Kanai et al., and U.S. Pat. No. 3,755,891 to Muckelroy et al., all of which are incorporated herein by reference.
Accordingly, it would be desirable to provide advantageous and efficient techniques for producing high performance, low cost, miniature drift tubes or other sensor structures for IMS devices on a large production scale.